This colour space is the de facto standard colour space for
computer data, unless some more specific colour space is explicitly
specified. Unless you know differently, any image data received
from the outside world is probably sRGB, and and data output is
probably expected to be sRGB.

Unfortunately, sRGB is a non-linear colour space, so it is not
feasible to perform arithmetic in it directly. (The sRGB colour
space basically standardises the defective non-linear behaviour of
obsolete CRT display technology.)